1. Field of the Invention
Embodiments of the invention are generally related to an apparatus and method for minimizing deposition on the bevel and backside of a substrate in an electrochemical deposition cell.
2. Description of the Related Art
Metallization of high aspect ratio 90 nm and smaller sized features is a foundational technology for future generations of integrated circuit manufacturing processes. Metallization of these features is generally accomplished via an electrochemical plating process. However, electrochemical metallization of these features presents several challenges to conventional plating methods and apparatuses. For example, one challenge associated with conventional plating apparatuses and methods is deposition on the bevel or backside of the substrate. Although deposition on the bevel or backside of the substrate generally does not have a negative impact on the production surface of the substrate, the bevel or backside deposition must be removed, requiring additional process steps that reduce substrate throughput.
Deposition on the bevel or backside of the substrate generally results from the electrical field that is used to drive the plating process having an electrical path to the bevel or backside of the substrate. Generally, this path extends around the top of the substrate supporting contact ring and toward the bevel or backside of the substrate in the direction of the electrical contact pins. Conventional plating cells have attempted to reduce this current path by utilizing a front side flange or front side seals configured to minimize edge and bevel deposition. However, these systems have not been successful in preventing bevel or backside deposition, as these frontside devices are not able to minimize the current path that extends around, i.e., over the back, of the substrate supporting contact ring.
Another challenge for conventional plating systems is bubble formation. For example, when a substrate is immersed into a plating solution, bubbles both adhere to the substrate surface and get trapped along the surface the substrate. These bubbles have been shown to subsequently cause plating defects that may render devices formed on the substrate inoperable.
Therefore, there is a need for an electrochemical plating cell and method for plating configured to minimize the electrical field path to the bevel and backside of the substrate. There is also a need for an electrochemical plating cell and method for plating configured to minimize the damage that can be caused by the presence of bubbles across the surface of the substrate.